Plant biostimulants represent an innovative and sustainable solution to address the challenges of the future agriculture, especially when they are used to improve yield and quality of staple crops. The objective of this research was to study, over three consecutive seasons, the effect of a novel fertilization plan (Thesis 2, T2) on the productivity and protein content of bread wheat (Triticum aestivum L.), as compared to the traditional fertilization pattern (Thesis 1, T1), commonly used in Tunisia. T2 was based on the use of a pre-sowing soil bioenhancer (SBE, commercially known as ‘Terios’) and a topdressing with foliar bio-stimulant (FBS, commercially known as ‘Celerios’), obtained by nanotechnology transformation of Y-CaCO3 minerals (called ‘vaterite’); while T1 was based on the use of diammonium phosphate (DAP) at pre-sowing and ammonium nitrate (AN) during the growing season. FBS was applied two times each season and at one rate (3 kg ha−1). In each farm and experimental year, the following traits were recorded: plant height (cm), whole aerial biomass (t DM ha−1), grain yield (t ha−1, 13% moisture content), harvest index, grain weight (mg), spike density (number of spikes per m2), grain protein content (%). T2 protocol slightly, but significantly, increased yield, yield components and grain protein content, while it decreased plant height at harvest. These results suggest that the use of FBS could be of great interest for the cultivation of bread wheat under Mediterranean climatic conditions, as it can make plant nutrients rapidly available even when the uptake from the soil is hindered by water scarcity.

Under the high temporal variability of the Mediterranean climate, the prompt emergence of wheat seedlings and early vigor are pivotal attributes, positively affecting the final grain yield. Phosphorus (P) fertilization at sowing is largely used in wheat cultivation to support the early-season growth and promote a more rapid crop establishment. While conventional farming can rely on a wide variety of synthetic fertilizers, the number of options available for the starter fertilization of organic wheat is restricted and many are often unsuitable. Nanotechnology applied to fertilizers could provide a valuable means to combat this issue. This study aimed to evaluate the starter effect of a granular soil bio-enhancer (SBE) on bread wheat grown in two locations of Northern Tunisia as compared to conventional fertilization with diammonium phosphate (DAP). The SBE was obtained by physically grinding phosphate rocks at a nanoscale level and further mixing it with azotobacters. Aerial dry biomass, plant height, crop density, tiller density, leaf area index (LAI), and leaf P concentration were determined up to 70 days after emergence (DAE) to assess the early vigor of wheat seedlings. The application of SBE before sowing resulted in a greater early vigor of wheat seedlings as compared to commercial DAP over three consecutive growing seasons. Specifically, the aerial dry biomass and the plant height at 7 DAE were found to have increased by 56% and 48%, respectively. LAI at 70 DAE was enhanced by 8.5%, while moderate percentage increases were detected for both crop and tiller density. Finally, wheat plants fertilized with SBE showed a significantly higher leaf P concentration than DAP-fertilized plants in 2020 and 2021 (+21% and +32%, respectively).